The present invention relates to waveform control circuits and, more particularly, to novel methods for operating programmable signal control circuits to provide a desired output therefrom.
In many forms of remotely-controlled systems, it is desirable to transmit information by means of varying the amplitude of a D.C. level or by varying a characteristic (amplitude, frequency, phase, pulse-width, etc.) of an A.C. waveform. Frequently, the circuit controlling the modulated characteristic of the signal requires many costly components, detracting from the advantageous use thereof in high-volume systems. In particular, with the present emphasis upon energy conservation it is desirable to provide a remotely-programmable lighting system, and especially such a system wherein maximum light level in an area can be set, such that individual users can not control the variable light output in their area to a greater value than the pre-established maximum. In such a system, it is also desirable that other values of light output, below the pre-established maximum, can be easily, and preferably linearly, set by the individual user. Further, it is highly advantageous that area lighting system output be under programmable control, such as from a microcomputer and the like at a central facility. Additionally, in such systems, the lighting loads are often connected to a powerline, that the control electronics be capable of being isolated from the relatively high-voltage powerlines for reasons of personal safety.
It is also highly desirable to be able to operate the signal characteristic (e.g. amplitude) control circuit in such a manner that immediate changes in lighting level can be effected, such as when the lighting is initially turned on or is turned off to a zero output value, yet still allow operation of the load with a gradual change in output between any selected pair of discrete levels. Accordingly, a programmable signal characteristic control circuit and methods for achieving abrupt and/or gradual changes in output level thereof, are highly desirable.